This proposal describes a supervised training program that will provide a foundation of knowledge in molecular biology necessary to embark on an independent research career in the field of liver growth and regeneration. The scientific goal is to characterize the structure and function of SL-314, a specific novel immediate-early gene which, although highly induced in the normal growth responses of liver regeneration and fibroblast proliferation, is constitutively expressed at a high level in H-35 hepatocellular carcinoma cells in culture. This gene was isolated through subtraction and differential screening of cDNA libraries from regenerating liver, insulin-stimulated H-35 hepatoma cells and serum-stimulated Balb/3T3 mouse fibroblasts. Five additional genes isolated using these methods were found to be rapidly induced in both regenerating liver and insulin-stimulated H-35 cells, and either constitutively expressed in insulin-stimulated H-35 cells, or expressed at significantly higher levels in stimulated H-35 cells relative to regenerating liver. These five genes may also become the subject of inquiry in this project. The Sanger dideoxy chain termination sequencing method, Northern and Southern blotting techniques, a cDNA expression system, promoter analysis assays, and tumorigenesis assays will all be used to analyze the structure, distribution, function, and carcinogenic potential of one of these genes. The majority of the effort will be directed toward the characterization of SL-314, which is of particular interest because it is highly induced in liver regeneration. However, if after initial studies, it becomes apparent that SL-314 is not as interesting as anticipated, the focus will shift to one of the other genes that have an abnormally high degree of expression in H-35 cells relative to regenerating liver. The scientific questions to be answered are, "What are the roles of these genes in the complex phenomenon of liver regeneration?", and "Can their premature activation and overexpression in hepatoma cells explain the malignant behavior exhibited by these cells?". Answers to these questions will advance our understanding of the control of liver growth and the biogenesis of cancer, and could well be important in the development of better therapeutic approaches in the fields of liver transplantation, fulminant hepatic failure, and developmental liver diseases.